The present invention relates to making parts out of composite material, and more particularly to making reinforcing fiber structures for such parts.
A field of application of the invention lies more particularly in making parts out of structural composite material, i.e. structural parts having fiber reinforcement that is densified with a matrix. Composite materials make it possible to make parts of overall weight that is less than the weight of the same parts when they are made out of metal material.
In the context of making fiber structures by three-dimensional weaving in order to constitute the fiber reinforcement of a composite material part, such as an aeroengine blade, it is necessary during the weaving of the structure to remove yarns both in the warp direction and in the weft direction in order to impart reductions in the thickness of the part, e.g. for the tang of a blade, so as to obtain a fiber preform that presents the almost final shape and dimensions of the blade (i.e. its “net shape”). During weaving, removing yarns leads to yarn layers appearing that are not woven (i.e. that are floated) and that are subsequently cut away during a second operation.
It is difficult and awkward to cut away the floats of each layer because of the lack of cohesion between the non-woven yarns belonging to a single layer. In order to perform cutting as close as possible to the outline of the preform but without damaging it, it is preferable to cut the yarns layer by layer, beginning with the layer present at the surface of the structure and continuing with the underlying layers. Such layer-by-layer cutting requires manual intervention by an operator who takes hold of and cuts the yarns in a given layer one by one.